2-Amino- and 2-alkylamino-3-cyano-5-pyridyl-pyridines are known e.g. from U.S. Pat. No. 4,362,734, East German patent Nos. 263,758; and 275,047, and from an article in, Die Pharmazie 44, 20, (1989). 2-aminoalkylamino-3-cyano-, 3-cyano-2-oxyaxlkoxy-, and 3-cyano-2-oxyalkylamino-5-(pyrid-4-yl)-pyridines, and 3-cyano-2-morpholino-5-(pyrid-4-yl)-pyridine and their cardiotonic action are described in European patent No. 200,024 A2.
Likewise, 2-chloro-3-cyano-, and 2-alkoxy-3-cyano-5-(pyrid-4-yl)-pyridines and the cardiotonic activity of the latter compound are described, for example, in, Pol. J. Pharmacol. 30, 707 (1978), and also in U.S. Pat. Nos. 4,264,603; 4,463,008; and Spanish patent No. 518,498).
Biologically active heterocyclic compounds are frequently also administered in the form of their pharmaceutically acceptable acid addition salts, such as in the form of their hydrochlorides, sulfates, acetates, fumarates, mesylates or tartrates, as described in German published patent application No. 2,637,600.
5,4'-bipyridine-mono-1'-oxides with functional groups in the 2- and/or 3-position have not previously been synthesized, except with the exception of the 1'-oxide of 3-amino-5-(pyrid-4-yl)-pyrid-2-one (amrinone), and its 3-acetamido analogs. Moderately positive inotropic effects were claimed for the 1'-oxide of amrinone in German published patent application No. 3,045,637. The 1'-oxide of 3-cyano-6-methyl-5-(pyrid-4-yl)-1,2-dihydro-pyrid-2-one (milrinone) was mentioned as a metabolite of this active ingredient by A. A. Alousi, et al., New Drug Animal, Cardiovasc. Drugs 3, page 269 (1985). There was no report of possible heart stimulating activities of the latter compound.